use more concise and foolproof patch-method

lib/open_project/plugins/acts_as_op_engine.rb

@@ -57,11 +57,10 @@ module OpenProject::Plugins
       # This looks for OpenProject::XlsExport::Patches::IssuesControllerPatch
       #  in openproject/xls_export/patches/issues_controller_patch.rb
       base.send(:define_method, :patches) do |patched_classes|
-        plugin_name = engine_name
+        plugin_module = self.class.to_s.deconstantize
         base.config.to_prepare do
           patched_classes.each do |klass_name|
-            plugin_module = plugin_name.sub(/^openproject_/, '').camelcase
-            patch = "OpenProject::#{plugin_module}::Patches::#{klass_name}Patch".constantize
+            patch = "#{plugin_module}::Patches::#{klass_name}Patch".constantize
             klass = klass_name.to_s.constantize
             klass.send(:include, patch) unless klass.included_modules.include?(patch)
           end
@@ -69,11 +68,10 @@ module OpenProject::Plugins
       end
 
       base.send(:define_method, :patch_with_namespace) do |*args|
-        plugin_name = engine_name
+        plugin_module = self.class.to_s.deconstantize
         base.config.to_prepare do
           klass_name = args.last
-          plugin_module = plugin_name.sub(/^openproject_/, '').camelcase
-          patch = "OpenProject::#{plugin_module}::Patches::#{klass_name}Patch".constantize
+          patch = "#{plugin_module}::Patches::#{klass_name}Patch".constantize
           qualified_class_name = args.map(&:to_s).join('::')
           klass = qualified_class_name.to_s.constantize
           klass.send(:include, patch) unless klass.included_modules.include?(patch)